Process of obtaining carbon black and hydrocarbons of more complex molecular structure by the pyrolytic dissociation of hydrocarbon gases and vapors



D. WILCOX Filed Dec.

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PROCESS OF OBTAINING CARBON BLACK AND HYDROCARBONS OF MORE COMPLEXMOLECULAR STRUCTURE BY THE PYROLYTIC DISSOCIATION OF HYDROCARBON GASESAND VAPORS lllllllllllll l July 4, 1933.

y INVENTOR.

Patented July 4, 1933 umTa offs TATEs PATENT OFFICE WILLIAM: D. WIL COXOF KANSAS CITY, MISSOURI PROCESS OI OBTAINING CARBON BLACK ANDHYDROCAR-BONS 01: MORE COH PLEx MOLECULAR STRUCTURE BY THE PYROLYTICDISSOOIATION OF 'HYDBOCARBON GASES AND VAIORS Application filed December6, 1930. Serial No. 500,582.

Over a 1011 period of years, primary distillation pro mote, chiefly ofthe methane series, given ofi in the carbonization of coal, have beencracked by contact with the highly heated walls of the retorts. and havepolymerized forming vapors of the benzol series, naphthalene, etc. Thatthese products are the result of subjection to high temperature andrecombination is well evidenced by their almost entire absence from theproducts obtained by carbonization at low temperature. Rather recentlyexperiments have been carried out for the most part under laboratoryconditions in which methane and its homologues have been subjected totemperatures similar to those which exist along the walls of a coal gasoven for a brief interval and the products of cracking collected. Theyare found similar to those obtained commercially by scrubbing coal gas.Cracking of gases at somewhat hi her temperatures to obtain carbonand/or hydrogen, according to the formula OH plus heat equals C plus 2Hhas been brought into commercial use. It is the purpose of my process toobtain condensible hydrocarbons together with finely divided carbon.Whileone combination of operating conditions is most favorable to theroduction of polymerization products, anot or more favorable to theevolution of solid carbon, my rocess embodies conditions of operation anprocedure by which both products are obtained in usable form and thevalue of total product thereby increased.

My process can be more readily understood by reference to theaccompanying diagram. A is a vertical conduit of refractory materialspreferably built in the form of an inverted U, B is an inlet for theintroduction of the hydrocarbon gases which are to be decomposed, E isthe outlet for these gases, C

' is an inlet throu h which a combustible mixture of gas an air isadmitted either to the conduit itself, in which event heat is imparteddirectly to the interior walls of the conduit by periodic combustion, orto flues within the enclosing walls of the conduit, in which eventheating is continuous and the heat which efi'ects dissociation must passinward through the enclosing walls as in the by-product coke oven, D isthe outlet for the combustion gases. Silica is the most suitablematerial for the lining of the conduit, both by reason of its highlyrefrac tory qualities and by reason of the fact thatit does not, as dometals, exercise a catalytic to obtain gas or carbon, to fill thedissociation chamber with checker brick to provide the media of heatabsorption and transfer. This I find to be highly disadvantageous so faras the recovery of carbon is concerned. In this arrangement or employingloosely piled refractory material there are horizontal surfaces andspaces outside the direct current of gas upon which the carbon settles,remains, and is consumed in the following blast period. I find that agreat increase in the proportion of carbon recovered may be effected byusing small vertical flues in place of checker brick. This alone is notadequate. The velocity of the gas must be sufficient to overcome thetendency of carbon recovery of the carbon evolved, the total: length oftravel of the gas treated was 41' feet, and there is reason to believethat some advantage will result from a further increase.

It will be noted that the combustion gases by which the contactingsurfaces are brought to a dissociating temperature are passed throughand from the dissociating unit in a direction counter current to thedirection of travel through this unit of the gases subjected todissociation. They fall in temperature durin this passage, though ivingup a part of t eir heat to the flue wa so that the temperatures createdare progressively less from the point where active combustion takesplace to the outlet. It follows from this that the gases subjected totreatment, in counter current flow are progressively in contact withmore highly heated surfaces in their passage through the dissociationchamber and are gradually brought to the temrature final y attained. Inthe drawing I ave indicated a robable range of temperature variation. Tis is illustrative only. The actual range of temperatures will vary withthe volume per minute of fuel gas and air introduced, the le h of travelas determined by the dimensions of the unit, the rate of travel asdetermined by velocity, and the len h in time of the reheatin period.

ere the carbon is recovere byslow deposition or by filtering the gasthrough cloth bags, the gas is so cooled that a portion of the volatilescondense upon the carbon making necessary its later subjection to acalcining process. For this reason I pass the gas issuing through Evthrough pipe F surrounded by a water jaclret, the amount of coolingwater relative to the volume of gas passing being so controlled as tocool the gas to around 900 F. At this temperature the polymerizationproducts remain gaseous. The gas is passed through electricalprecipitation unit G. The carbon is recovered free of volatiles andremoved from the base of the'unit by conve or H. The gas thenpassesthrough secondary cooler I. It may be found advlsable to introducea tar extractor between I and oil scrubber J to remove the heavier andmore readily condensible hydrocarbons. In J the as passes up countercurrent tooil sprayed from K. The benzol, naphthalene etc. are absorbedby the oil and pass out through-M, the stripped gas through Benzol isseparated from the oil by well known means. The gas may be furthertreated to obtain carbon and hydrogen, passed through an electric arcwith production of carbon, acetfylene and hydrogen, or it mai be burnedso ar as necessary tosup ly t e heat required for dissociation. en thegasses treated are rich in ethane, propane and butane the residue gaswill contain a lar e percentage of eglsylene usable in the pr notion ofmany use chemicals.

My process may be advantageously employed using natural gas, crackingstill gases, oil vapors, or a rich coal gas. The best results areobtained within a temperature range of 1800 to 2150 F. When a conduitsuch as shown is of extended length better results in the proportion ofheat absorbed from the heating gas and made useful are ohgases enterneed not be brought to a dissociation temperature. It may, andpreferably will be, employed to preheat the gas prior to its beingbrought in contact with the surfaces heated to a tempe1..ture in excessof 1800 F. Referring to the drawing, it will be seen that thetemperature of the conduit is progressively increased from 1200 F. to amaximum temperature of 2250 F. The drawing also shows, diagrammatically,the temperatures of various zones in the conduit, such as 1200 F. to1400 F., 1400 F. to 1650 F., 1650 F. to 1950 F. and 1950 F. to 2250 F.,the temperatures increasing in the direction of the flow of the run gasthrough the conduit. The 0 timum temperature of operation in any unitmust be determined by operating experience. The higher homologues ofmethane are dissociated at somewhat lower temperatures, and hence thetemperatures em loyed will be determined in some degree by t ecomposition of the gases treated. Maximum temperatures imparted to theheated contact surfaces will be within the range 1900 to 2200 F., thegas will be somewhat less heated. The time of contact of the gas withthe surfaces heated to these temperatures will range from one to threeseconds. Shorter time of contact is more favorable to the production ofpolymerization products, longer to the production of carbon andhydrogen. Longer contact is permissible where the temperatures arerelatively low. It is quite well established that continued subjectionto high temperatures causes the particles of carbon to sinter togetherdecreasing the average fineness of division and imparting to the producta grayish tint. With high velocity and only a brief time of exposure toheat, the carbon recovered will be of a darker color and more nearlyapproaching the particle size of channel process black. This fact insome degree offsets the smaller recovery as compared with the results ofoperation at higher temperatures and with longer time of contact. It isnot believed possible to obtain maximum recoveries of polymerizedproducts without the employment of temperatures at which some carbon ismade.

What I claim as new and desire to protect by the issuance to me ofLetters Patent is-- 1. The process of obtaining carbon black andhydrocarbons of more complex molecular structure by the pyrolyticdissociation of hydrocarbon gases and va ors which comprises passingthehydrocar on gases in contact with the refractory interior surfaces ofa conduit which are heated within a maximum range of 1800 to 2200 F.,with a time of contact with the surfaces so heated within the rangeofone to three seconds, cooling the no-lanai issuing gas to atemperature at which the condensible hydrocarbons remain vaporous, re-

covering the carbon from the gas, further cooling it and extracting thecondensible hydrocarbons therefrom.

2. The process of obtaining carbon black and hydrocarbons of morecomplex molecular structure by the pyrolytic dissociation of hydrocarbongases and vapors which comprises 310 heating the interior of arefractory walled conduit by maintaining a periodic combustion thereinto a maximum temperature within the range 1800 to 2200 F., andthereafter passing'hydrocarbon gases through the conduit in a directioncounter current to the travel of the heating gases and contacting themwith the surfaces so heated within the range 186W to 2200 F. for aperiod of time within the range one to three seconds, and thereaftercooling the gas to a temperature at which the condensible hydrocarbonsremain vapors, recovering the carbon, further cooling the gas andabsorbing out the condensible components of the gas.

% 3. The steps in the process of obtaining carbon black and hydrocarbonsof more complex molecular structure by the pyrolytic dissociation ofhydrocarbon gases and vapors which comprises passing the hydrocarbon sogases in contact with the interior surfaces of a conduit heated to amaximum temperature.

within the range 1800 to 2200 i giving to the gases a time of contactwith the surfaces so heated within the range of one to three as seconds.

4c. The steps in the process of obtaining carbon black and hydrocarbonsof more complex molecular structure by the pyrolytic-dis sociation ofhydrocarbon gases and vapors so which comprises heating the refractoryin-' terior surfaces of a conduit to a maximum temperature within therange 1800" to 2200 F. by periodically passin hot combustion gasesthrough the conduit, and thereafter as passing hydrocarbon gases throughthe conduit in a direction counter current to the direction of travelof? the heatinggases, contacting them with the surfaces heated withinthe range 1800 to 2200 F. for a period of so from one to three seconds.i

p 5. The process of obtainin carbon together with benzol and other'hyrocarbons of more complex molecular structure by the pyrolyticdissociation of hydrocarbon gases as and vapors which comprises passingthe gases through a conduit, the interiorsuriaces of which are heated toa maximum temperature within the range 1800 to 2200 F, contacting themwith the surfaces so heated for a $01 period of one to three seconds,cooling the gases to a temperature in excess of that at which thepolymerized products condense, removingthe carbon, further cooling theuses, absorbing out and recovering the con ensible vapors,

6. The process of obtaining carbon black together with benzol and otherhydrocarbons or more compleximolecular structure by the pyrolyticdissociation of hydrocarbon gases and vapors which comprises heating theinterior of a refractory walled conduit by periodically burningcombustible gas therein to a maximum temperature within the range 1800to 2200" F, then passing'hydrocarbon gases through the conduit in adirection counter current to the travel of the heating gases at a rateof flow which ofisets the tendency of the carbon to adhere to the wallsand with a contact of the uses with the more highly heated surfaces oithe conduit for a period or one to three seconds, partially cooling theissuing gas, recovering the carbon therefrom, further cooling andabsorbing out and recovering the condensible hydrocarbons.

7f The process of obtaining carbon black, benzol and other hydrocarbonsof more complex molecular structure by the pyrolytic dissociation ofhydrocarbon gases and vapors which comprises heating the interior of aconduitto a maximum temperature within the range 1800 to 2200 F. bymeans of heat conducted from fines adjacent to the conduit andsimultaneously passing hydrocarbon gases and vapors through the conduitat a rate of travel which brings them in contact with the surfacesheated within therange of temperature stated for a period ot one tothree seconds, withdrawing the heated gases, cooling them to atemperature at which the condensible volatiles remain vapors, removingthe carbon formed, further cooling the gases absorbing out andrecovering the condensi le components of the gas.

8. The steps in the process of obtaining carbon black, benzol and otherhydrocarbons of more complex molecular structure by the pyrolyticdissociation or" hydrocarbon gases and vapors which comprises heatingthe interior surfaces of a conduit by means of heat conducted throughthe walls oi: the conduit from an external source to a maximumtemperature within the conduit of from 180 0 to 2200 F. andsimultaneously passing bydrocarbon gases or vapors through the conduitat a rate of travel which brings them in contact with the surf-acesheated within the temperatures stated for from one to three secends.

9. The steps in the process of obtaining carbon black together withbenzol and other hydrocarbons of more complex molecular structure by thepyrolytic dissociation of hydrocarbon gases and vapors which comprisespassing the hydrocarbon gases through a conduit of refractory materials,the interior surfaces of which are heated to maximum temperatures withinthe range 1800" to 2200 F, at such a rate of flow as prevents the carbonevolved from adhering to the interior races of the conduit, and whichpermits carbon black,

a contact of the hydrocarbon gases with the surfaces so heated for aninterval within the range of one to three seconds.

10. The steps inthe rocess of obtaining carbon black together withbenzol and other hydrocarbons of more complex molecular structure bythedissociation of hydrocarbon gases and vapors which comprisescontacting the gases with refractory surfaces heated to a maximumtemperature within the range 1800 to 2200 F., durin from one to threesecon s.

11. The ste s in the process of obtaining henzol and other hydrocarbonsof more complex molecular structure by the dissociation of hydrocarbonases and va ors which comprises heating re ractory sur aces to temeratures within the range 1800 to 2200 E, contacting the hydrocarbongases a time interval of with these surfaces for a time interval of oneto three seconds, and immediately thereafter coolin the gases to a temerature of 900 F.

12. he process of obtaining carbon black, benzol and other hydrocarbonsof more complex molecular structure by the dissociation of hydrocarbongases and vapors which comprises heating refractory surfaces to atemperature within the ran e 1800 to 2200 F., contacting the hydrocar ongases with these surfaces for a time interval of one to three seconds,immediately cooling the gases to a temperature of 900 F., extracting thecarbon, further cooling the gases and absorbing out and recovering thecondensible hydrocarbons.

In witness whereofI have afiixed my signature.

WILLIAM D. WILCOX.

